Method to detect and remove gas bubbles from molten substrate to prevent hollow fiber formation

ABSTRACT

Method and apparatus for removing bubbles from a molten substrate. The molten substrate from a furnace passes through a downtube to reach additional manufacturing tools, such as an extrusion bushing. One or more ultrasonic sensors are arranged along the downtube. The ultrasonic sensor(s) transmit ultrasonic energy into the molten substrate and measure a characteristic of the ultrasonic energy, such as a propagation time for the ultrasonic energy to be reflected back to the ultrasonic sensor(s). A bubble is detected when a change in the characteristic of the ultrasonic energy is detected. When a bubble is detected, flow through the downtube is diverted to a duct to remove a slug of molten substrate that includes the bubble.

BACKGROUND

The present invention relates to fiber formation, and more specifically,to fiber formation from a molten substrate.

Printed circuit boards are often made with a mat of woven glass fiberswithin a cured resin substrate. The glass fibers provide structuralreinforcement for the resin. The glass fibers are formed by extrudingmolten glass. Occasionally, a bubble in the molten glass is carried intothe extrusion process. In such cases, the bubble can be contained in aformed thread in an elongated form. As a result, the thread includes ahollow region.

If such a hollow thread is used in a printed circuit board, the hollowthread could cause a circuit failure, such as a short circuit or an opencircuit. For example, holes or vias are often drilled through a printedcircuit board. If such a hole is drilled through a hollow thread, aconductive circuit material could travel through the hollow portion ofthe thread, forming a conductive anodic filament (CAF). The CAF couldinadvertently connect two circuit elements that are not supposed to beconnected, resulting in a short circuit or bad circuit.

As the density of circuit elements on printed circuit boards increases,the likelihood that a hollow thread will cause a circuit failure alsoincreases. Thus, avoiding the use of hollow threads in printed circuitboards is important to reduce the number of faulty circuit boards.Currently, random samples of formed glass threads are pulled fromproduction and checked for hollow threads. In the event a hollow threadis discovered, the sample and at least a portion of a batch from whichthe sample came are discarded. Such random sampling is imperfect becausea hollow thread could make it through the process undetected.Furthermore, such a process could result in large amounts of scrapthread when thread is discarded due to a discovered hollow thread.

SUMMARY

According to one embodiment of the present invention, an apparatus forsupplying a molten substrate includes a downtube adapted to receive themolten substrate at an upstream end of the downtube and to distributethe molten substrate at a downstream end of the downtube. The apparatusalso includes an ultrasonic sensor arranged along the downtube. Theultrasonic sensor is operable to detect bubbles in the molten substratein the downtube. The apparatus also includes a duct arranged along thedowntube. The duct is operable to remove a slug of the molten substratefrom the downtube upon the ultrasonic sensor detecting a bubble in themolten substrate.

According to one embodiment of the present invention, an apparatus forforming fibers from a molten substrate includes a furnace operable tomelt a substrate supply into a molten substrate. The apparatus alsoincludes a downtube that includes an upstream opening and a downstreamopening. The upstream opening is in fluid communication with an outletof the furnace. The downtube includes an ultrasonic sensor arrangedalong the downtube. The ultrasonic sensor is operable to detect bubblesin the molten substrate in the downtube. The downtube also includes aduct arranged along the downtube. The duct is operable to remove a slugof molten substrate upon the ultrasonic sensor detecting a bubble in theslug of molten substrate. The apparatus also includes a bushing in fluidcommunication with the downstream end of the downtube, wherein thebushing includes a plurality of extrusion ports therethrough. Theapparatus also includes a winding apparatus operable to pull threads ofmolten substrate through the extrusion ports and form the threads into awinding of threads.

According to one embodiment of the present invention, a method forremoving bubbles from a molten substrate includes transmittingultrasonic energy into a downtube through which a molten substrate isflowing. The method also includes detecting a characteristic of theultrasonic energy. The method also includes, upon detecting apredetermined change to the characteristic of the ultrasonic energy,diverting a slug of molten substrate from the flow of molten substratein the downtube to a duct.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1A is a schematic depiction of an apparatus for melting glass andextruding the glass into glass fibers;

FIG. 1B is a detailed schematic depiction of a winding portion of theapparatus shown in FIG. 1A;

FIG. 2 is a schematic depiction of a portion of an apparatus, accordingto at least one embodiment, that includes a downtube, an ultrasonicsensor arranged along the downtube to detect a bubble in molten glass,and a duct for removing a slug of molten glass that contains the bubble;

FIG. 3 is a schematic depiction of an apparatus, according to at leastone embodiment, that includes a downtube, a first ultrasonic sensorarranged along the downtube to detect a bubble in molten glass, a ductfor removing a slug of molten glass that contains the bubble, and thatoptionally includes a second ultrasonic sensor in the duct and/or anultrasonic sensor downstream of the duct arranged along the downtube;

FIG. 4A is a schematic view of an apparatus, according to at least oneembodiment, that includes a downtube and a flapper valve arranged in thedowntube, wherein the flapper valve is arranged in a position to directmolten glass through the downtube;

FIG. 4B is a schematic view of the apparatus of FIG. 4A, in which theflapper valve is arranged in a position to direct the molten glass intoa duct;

FIG. 5A is a side view of a downtube, according to at least oneembodiment, having an array of ultrasonic sensors arranged around thedowntube and four ducts arranged around the downtube downstream of theultrasonic sensors;

FIG. 5B is a top view of the downtube of FIG. 5A;

FIG. 6 is a schematic view of an apparatus, according to at least oneembodiment, having two downtubes connecting a furnace to a bushing forextruding glass fibers, wherein each downtube has a dedicated duct forremoving a slug of molten glass containing a bubble;

FIG. 7A is a chart of exemplary data from a ultrasonic sensors detectinga bubble in molten glass; and

FIG. 7B is a chart of exemplary data from an array of two ultrasonicsensors detecting a bubble in molten glass.

DETAILED DESCRIPTION

In the following, reference is made to embodiments presented in thisdisclosure. However, the scope of the present disclosure is not limitedto specific described embodiments. Instead, any combination of thefollowing features and elements, whether related to differentembodiments or not, is contemplated to implement and practicecontemplated embodiments. Furthermore, although embodiments disclosedherein may achieve advantages over other possible solutions or over theprior art, whether or not a particular advantage is achieved by a givenembodiment is not limiting of the scope of the present disclosure. Thus,the following aspects, features, embodiments and advantages are merelyillustrative and are not considered elements or limitations of theappended claims except where explicitly recited in a claim(s). Likewise,reference to “the invention” shall not be construed as a generalizationof any inventive subject matter disclosed herein and shall not beconsidered to be an element or limitation of the appended claims exceptwhere explicitly recited in a claim(s).

FIGS. 1A and 1B illustrate an apparatus 100 for forming glass threads116 from a molten glass source. The apparatus 100 starts with rawmaterials 102, such as a dry mixture of silicas, limestone, clay, andboric acid. The raw materials 102 pass-through measuring devices 104that distribute the raw materials in the proper amounts or proportions.The raw materials 102 then pass through a mixer 106, and the mixed rawmaterials 102 are then dropped into a furnace 108. The furnace 108 meltsthe raw materials to a temperature of between 1370° C. and 1540° C. toform a molten glass mixture. The molten glass mixture flows into arefiner 110 where the molten glass mixture cools to a temperature ofbetween 1340° C. and 1425° C. The molten glass mixture homogenize as itflows into the refiner 110. Additionally, gas bubbles 112 in the moltenglass mixture (e.g., caused by entrapment of air or the release of gasduring decomposition of water, carbonates, and/or organic matter in theraw materials) travel to the surface of the molten glass mixture refiner110. After the refiner 110, the molten glass mixture passes into aforehearth 114 where the molten glass mixture cools to a temperature ofbetween 1260° C. and 1371° C. In the forehearth 114, any remainingbubbles 112 may float to the surface of the molten glass mixture,resulting in a molten glass mixture 130 that is ready to be extrudedinto glass threads.

The illustrated apparatus 100 includes three bushings 120 arranged underthe forehearth 114. In various embodiments, the apparatus 100 caninclude more or fewer than three bushings 120. The molten glass 130travels in the direction of arrow A (shown in FIG. 1B) into the bushings120. The bushings 120 include nozzles 122 through which the molten glasscan be extruded as individual glass threads 134. Optionally, theindividual glass threads 134 pass through a sizer 140, which finalizesthe diameter of the individual glass threads 134. The individual glassthreads 134 can be formed into a glass strand 116 by a strand former142, which braids, twists, and/or otherwise combines the individualglass threads 134. The glass strand 116 can then be wound onto winders118. The winders 118 include a rotating spool 146. A traversingmechanism 144 can move in the direction of arrows Z to laterallydistribute the glass strand 116 about the spool 146. For example, theglass strand 116 can be arranged on the spool 146 in a crisscross orwoven pattern 150.

In various aspects, the process of forming the glass strand 116 isperformed in a continuous manner, meaning that a spool of the glassstrand is formed on the spool 146 until the spool 146 is full orotherwise reaches a predetermined size.

As discussed above, occasionally, a gas bubble 132 can remain entrappedin the molten glass mixture 130. When the bubble 132 reaches one of thenozzles 122 in the bushing 120, the gas bubble can be extruded into anelongated hollow 132′ within an individual glass thread 134. Asdiscussed above, such an elongated hollow 132′ in the thread 134 couldcause an electrical failure of a printed circuit board.

FIG. 2 illustrates an embodiment of an apparatus 200 in which a downtube230 is arranged between a forehearth 250 and a bushing 256 such thatmolten glass 252 passes down through the downtube 230 in the directionof arrow B to reach the bushing 256. The apparatus 200 includes anultrasonic sensor 202 arranged along the downtube 230. The ultrasonicsensor 202 could be arranged along a designated detection region 208 ofthe downtube 230. The ultrasonic sensor 202 includes an ultrasonictransducer 206 and an ultrasonic receiver 204. The ultrasonic transducer206 outputs ultrasonic energy into the downtube 230 (indicated by waves240) and the ultrasonic receiver 204 measures a characteristic of theultrasonic energy 240. As shown in FIG. 2, the ultrasonic transducer 206is located downstream relative to the ultrasonic receiver 204. Invarious embodiments, the ultrasonic transducer 206 could be locatedupstream relative to the ultrasonic receiver 204. As discussed ingreater detail below, the characteristic of the ultrasonic energy 240could be a propagation time for the ultrasonic energy to leave theultrasonic transducer 206, travel across the downtube 230, reflect offof a far wall of the downtube 230, travel across the downtube 230 asecond time, and then be detected by the ultrasonic receiver 204. In theevent that a bubble 254 in the molten glass 252 travels through thedowntube 230, the bubble 254 can alter the characteristic of theultrasonic energy 240. For example, the bubble 254 could cause at leastsome of the ultrasonic energy 240 to be reflected back toward theultrasonic receiver 204 instead of reflecting off of the far wall of thedowntube 230. As a result, that ultrasonic energy 240 would have ashortened propagation time. In various embodiments, the characteristicof the ultrasonic energy 240 could be any aspect of the ultrasonicenergy that changes due to the bubble in the molten glass 252. Otherexamples of characteristics of the ultrasonic energy include a frequencyof the ultrasonic energy, a phase of the ultrasonic energy, and amagnitude of the ultrasonic energy. In the event that a bubble 254 inthe molten glass 252 is detected in the downtube 230 by the ultrasonicsensor 202, a slug of the molten glass 252 containing the bubble 254 canbe directed into a duct 210 arranged along the downtube at a locationthat is downstream of the detection region 208. The duct 210 isselectively operable to only remove molten glass 252 from the downtube230 when a bubble 254 is detected. Operation of the duct 210 can betimed relative to the detection of the bubble 254 based on, among otherthings, a flow rate of the molten glass 252 through the downtube in thedirection of arrow B. For example, suppose that the duct 210 is arranged1 inch below the detection region 208 of the downtube 230 and the moltenglass is flowing at a rate of a half inch per second. In such aninstance, the duct 210 would be operated two seconds after a bubble 254is detected in the molten glass 252. Furthermore, suppose that thedetection region 208 is two inches in length along the downtube 230 anda detected bubble 254 could be anywhere within that two inch length. Insuch an instance, a bubble at the bottom of the detection region 208would take two seconds to reach the duct 210 and a bubble at the top ofthe detection region 208 would take six seconds to reach the duct 210.In this instance, the duct 210 would begin operating two seconds after abubble 254 is detected in the detection region 208 and will continue tooperate for four seconds thereafter to capture entire slug of moltenglass 252 in which the bubble 254 could be contained.

In the event a bubble 254 is not detected in the molten glass 252, themolten glass 254 flows in the direction of arrow B to the bushing 256.The bushing 256 forms individual glass threads 258. Optionally, theindividual glass threads 258 pass through a sizer 260, which finalizesthe diameter of the individual glass threads 258. The individual glassthreads 258 can be formed into a glass strand 264 by a strand former262, which braids, twists, and/or otherwise combines the individualglass threads 258. The glass strand 264 can then be wound onto arotating spool 266. For example, the glass strand 264 can be arranged onthe spool 266 in a crisscross or woven pattern 268.

As will be discussed in greater detail below, a downtube (e.g., downtube230) could include an additional ultrasonic sensor (e.g., ultrasonicsensor 202) located downstream of the duct 210. In the event a bubble254 is not captured by the duct 210, the bubble 254 would pass throughthe bushing 256 and be formed into an individual glass thread 258, asdiscussed above. In various embodiments, an apparatus, such as apparatus200 shown in FIG. 2, could include a marking module 220. The markingmodule 220 could spray a paint, such as a fluorescent or fluorescingpaint, onto the glass strand 264 for a period of time after a bubble 254is detected downstream of the duct 210. The period of time could bepredetermined or could be calculated to mark the glass strand 264 alonga length in which the elongated bubble 132′ (shown in FIG. 1A) isincluded or could be included. Thereafter, potentially defectiveportions of the glass strand 264 can be identified by looking for themarked portions. The identified portions could then be removed.

In various circumstances, diverting a slug of molten glass 252 to theduct 210 to remove a bubble 254 could temporarily decrease the supply ofmolten glass 252 to the bushing 256. In various embodiments, after aslug of molten glass 252 has been removed via the duct 210, the windingoperations performed at the bushing 256 through the winder can be sloweddown (i.e., the individual glass threads 258 and strand 264 can beformed at a slower rate) for a period of time to allow the downtube 230to refill with molten glass 252. In various other embodiments, thegeometry of the downtube 230 and the viscosity of the molten glass 252could cause the downtube 230 to refill with molten glass at a fasterrate than the bushing 256 uses the molten glass 252 from the downtube230. As a result, the winding operations could continue at a single rateboth during normal operations and operations when the duct 210 isremoving a slug of molten glass 252.

FIG. 3 illustrates a portion of an apparatus 300 according to at leastone embodiment for forming glass strands. The apparatus 300 includes afurnace 302 (e.g., a furnace, refiner, and forehearth) with molten glass304 therein. The molten glass 304 travels into a downtube 340 in thedirection of arrow D. The downtube 340 includes a first ultrasonicsensor 306 arranged along the downtube 340. As discussed above, theultrasonic sensor 306 includes an ultrasonic transducer 308 andultrasonic receiver 310 that are used to detect bubbles in the moltenglass 304. The ultrasonic sensor 306 can be in communication with acontroller 332 that controls a valve 330. The valve 330 opens and closesa fluid path to the duct 334. In the event that the ultrasonic sensor306 detects a bubble in the molten glass 304, the controller 332 canopen the valve 330 to allow the molten glass 304 to flow into the duct334 in the direction of arrow F. The duct 334 can be in communicationwith a vacuum source 324 such that when the valve 330 is opened, a slugof molten glass 304 in the downtube 340 is siphoned or sucked into theduct 334. The size or volume of the slug of molten glass 304 that issiphoned or sucked from the downtube 340 is determined at least in partby the length of time the valve 330 is opened and/or the magnitude ofthe vacuum provided by the vacuum source 324. In various embodiments,molten glass that is removed from the downtube 340 through the duct 334can be returned to the furnace 302, as indicated by arrow G. The furnace302 can reheat the molten glass removed by the duct 334. The reheatingof the molten glass 304 may remove the bubble, as discussed above withreference to FIG. 1A. In various other embodiments, the molten glassthat is removed from the downtube 340 through the duct 334 could bediscarded or otherwise recycled.

In various embodiments, the duct 334 optionally includes a secondultrasonic sensor 318 downstream of the valve 330 that is also incommunication with the controller 332. The second ultrasonic sensor 318includes an ultrasonic transducer 320 and an ultrasonic receiver 322 todetect a bubble in the molten glass 304 in the duct 334. In the eventthat the first ultrasonic sensor 306 detects a bubble in the moltenglass 304 and the valve 330 is opened, the second ultrasonic sensor 318can be used to detect the bubble in the duct 334. After the bubble hasbeen detected in the duct 334 by the second ultrasonic sensor 318, thevalve 330 can be closed by the controller 332. In various embodiments,the controller 332 does not close the valve 330 until the secondultrasonic sensor 318 detects the bubble and then no longer detects thebubble, meaning the entirety of the bubble has passed into the duct 334.

In various embodiments, the downtube 340 optionally includes a thirdultrasonic sensor 312 downstream of the duct 334. The third ultrasonicsensor 312 includes an ultrasonic transducer 314 and an ultrasonicreceiver 316 to detect a bubble in the molten glass 304 flowing throughthe downtube 340 in the direction of arrow E after the duct 334. Asdiscussed above, in the event a bubble passes through the downtube 340in the direction of arrow E, the bubble could cause a hollow glassthread. The third ultrasonic sensor 312 could be in communication withthe marking device 220, discussed above with reference to FIG. 2, andthe marking device 220 could mark the individual glass threads 258and/or the glass strand 264 in response to the third ultrasonic sensor312 detecting a bubble in the molten glass 304.

FIGS. 4A and 4B illustrate a portion of another apparatus 400 accordingto various embodiments. The apparatus 400 includes a downtube 402 with aflapper valve 406 or the like arranged therein. As shown in FIG. 4A, theflapper valve 406 is usually positioned such that it blocks the duct 404and molten glass 252 in the downtube 402 travels in the directions ofarrows D and E. In the event that the ultrasonic sensor 306 detects abubble in the molten glass 252, a controller 410 can move the flappervalve 406′ to the position shown in FIG. 4B such that the flapper valve406′ blocks the downstream portion of the downtube 402 and the moltenglass 252 is directed in the arrows D and F into the duct. By providinga flapper valve 406 or the like in the downtube and in the flow path ofthe molten glass 252, the flow of molten glass 252 may be diverted intothe duct 404 (in the direction of arrow F) without requiring suction orvacuum supply, discussed above.

FIGS. 5A and 5B illustrate a portion of another apparatus 500 accordingto various embodiments. The apparatus 500 includes a downtube 502 thatincludes multiple ducts arranged around a perimeter (e.g., acircumference) of the downtube 502. In this exemplary embodiment, thedowntube 502 includes a first duct 530, a second duct 532, a third duct534, and a fourth duct 536. The first duct 530, the second duct 532, thethird duct 534, and the fourth duct 536 are spaced apart by 90° from oneanother about the perimeter of the downtube 502. The downtube 502 alsoincludes an array of ultrasonic sensors arranged upstream of the ducts530, 532, 534, and 536. In this exemplary embodiment, the downtube 502includes a first ultrasonic sensor 504, a second ultrasonic sensor 510,a third ultrasonic sensor 516, and a fourth ultrasonic sensor 522arranged around a perimeter (e.g., a circumference) of the downtube 502.Each ultrasonic sensor includes an ultrasonic transducer and ultrasonicreceiver. For example, the first ultrasonic sensor 504 includes a firstultrasonic transducer 506 and a first ultrasonic receiver 508. Asanother example, the second ultrasonic sensor 510 includes a secondultrasonic transducer 512 and a second ultrasonic receiver 514. Asanother example, the third ultrasonic sensor 516 includes a thirdultrasonic transducer 518 any third ultrasonic receiver 520. In theexemplary embodiment, the ultrasonic sensors 504, 510, 516, and 522 arealigned with respective ones of the ducts 530, 532, 534, and 536. Invarious other embodiments, the ultrasonic sensors could be arranged outof alignment with the ducts.

In the exemplary apparatus 500, the four ultrasonic sensors 504, 510,516, and 522 divide the downtube 502 into four detection regions, whichhave boundaries indicated by dashed lines 550 and 552 and labeled “M,”“N,” “O,” and “P” in FIG. 5B. The array of ultrasonic sensors around thedowntube 502 can be used to identify a detection region or detectionregions in which a bubble 254 in the molten glass 252 is located. Acontroller 560 can operate valves in the duct(s) that are closest to thedetected location of the bubble. For example, referring to FIG. 5B, if abubble is detected in the molten glass 252 in detection region “M,” avalve 540 in the first duct 530 can be opened to siphon at least a slugof molten glass 252 located in region “M” into the first duct 530,indicated by arrow G. As another example, if a bubble is detected inregion “N,” a valve 542 in the second duct 532 can be opened to siphonat least a slug of molten glass 252 located in region “N” into thesecond duct 532, indicated by arrow H. As another example, if a bubbleis detected in region “O,” a valve 544 in the third duct 534 can beopened to siphon at least a slug of molten glass 252 located in region“O” into the third duct 534, indicated by arrow I. As another example,if a bubble is detected in region “P,” a valve 546 in the fourth duct536 can be opened to siphon at least a slug of molten glass 252 locatedin region “P” into the fourth duct 536, indicated by arrow J. In variouscircumstances, a plurality of valves could be opened to siphon moltenglass 252 from the downtube 502. For example, a bubble 254 in the moltenglass 252 could span multiple detection regions. To illustrate, supposethat a bubble 254 is detected in the molten glass 252 and that thebubble 254 is partially located in detection region “N” and partiallylocated in detection region “O.” In such a circumstance, the valve 542in the second duct 532 and the valve 544 in the duct 534 could both beopened to extract at least a slug of molten glass 252 located in regions“N” and “O.”

As discussed above, in various circumstances, removing a slug of moltenglass from the downtube could result in a momentary interruption in thesupply of molten glass 130 to the bushing 256. FIG. 6 illustrates aportion of an apparatus 600 that includes a forehearth 620 in fluidcommunication with a bushing 622 via a first downtube 602 and a seconddowntube 602. The first downtube 602 includes an ultrasonic sensor 306arranged along the downtube 602 and a duct 606 arranged downstream ofthe ultrasonic sensor 306. The duct 606 includes a valve 610 that can beopened by a controller 614 to siphon a slug of molten glass 252traveling through the downtube 602 in the direction indicated by arrow Sin the event that the ultrasonic sensor 360 detects a bubble in themolten glass 252 traveling through the first downtube 602. The seconddowntube 604 also includes an ultrasonic sensor 306 arranged along thedowntube 604 and a duct 608 arranged downstream of the ultrasonic sensor306. The duct 608 includes a valve 612 that can be opened by thecontroller 614 to siphon a slug of molten glass 252 traveling throughthe downtube 604 in the direction indicated by arrow T in the event thatthe ultrasonic sensor 306 detects a bubble in the molten glass 252traveling through the second downtube 604.

Under normal operation, the first downtube 602 supplies the bushing 622with molten glass, as indicated by arrow W, and the second downtube 604supplies the bushing 622 with molten glass, as indicated by arrow X. Inthe event that a bubble is detected in the molten glass travelingthrough one of the downtubes, the other downtube could continue tosupply molten glass 252 to the bushing to 622. For example, suppose thata bubble is detected in the molten glass 252 by the ultrasonic sensor306 arranged in the first downtube 602 and the controller 614 operatesthe valve 610 to remove a slug of molten glass 252 from the firstdowntube 602. In such a scenario, molten glass 252 would continue toflow uninterrupted through the second downtube 604 in the direction ofarrow X to the bushing 622. As another example, suppose that a bubble isdetected in the molten glass 252 by the ultrasonic sensor 306 arrangedin the second downtube 604 and the controller 614 operates the valve 612to remove a slug of molten glass 252 from the second downtube 604. Insuch a scenario, molten glass 252 would continue to flow interruptedthrough the first downtube 602 in the direction of arrow W to thebushing 622.

As discussed above, the ultrasonic sensors can detect a bubble in themolten glass by detecting changes to one or more characteristics of theultrasonic energy traveling through the molten glass. For example, anultrasonic sensor could measure a propagation time characteristic forthe ultrasonic energy by emitting ultrasonic energy using an ultrasonictransducer and detecting when the ultrasonic energy returns (e.g., isreflected back) to the ultrasonic sensor using an ultrasonic receiver.The amount of time from when the energy is emitted to when the energy isdetected is the propagation time. FIG. 7A illustrates a graph 700showing measured propagation time 702 (measured by an ultrasonic sensor)on a vertical axis and time 704 on the horizontal axis. The ultrasonicsensor may periodically emit ultrasonic energy and detect itspropagation time. For example, the ultrasonic sensor could emit anddetect the ultrasonic energy once per second (i.e., one Hertz), tentimes per second (i.e., 10 Hz), or a different interval. As shown inFIG. 7A, for a first period of time 710, a first series of data points716 for the ultrasonic sensor have a propagation time 706 of a firstduration. The first period of time 710 is an expected period of timerequired for ultrasonic energy to be transmitted by an ultrasonictransducer, travel across the downtube, reflect off a far wall of thedowntube, travel across the downtube again, and be received by anultrasonic receiver. Then, for a second period of time 712, a secondseries of data points 718 for the ultrasonic sensor have a propagationtime 708 of a second duration. Then, for a third period of time 714, athird series of data points 720 for the ultrasonic sensor have apropagation time 706 of the first duration. The period of time 712 inwhich the propagation time 708 is of the second duration could indicatethe presence of a bubble in the molten glass. For example, boundaries ofthe bubble could reflect the ultrasonic energy back to the ultrasonicsensor sooner (i.e., a shorter period of time than the expected periodof time) than if the ultrasonic energy travels all the way across thedowntube to a far wall then reflects back. The third period of time 714in which the propagation time 706 has returned to the first duration(i.e., the expected period of time) could indicate that the bubble inthe molten glass is no longer being detected.

In various embodiments, a length of time of the second period of time712 could be used to estimate the size of the bubble. For example,suppose that the molten glass is moving through the downtube at a speedof a half inch per second and that the length of time of the secondperiod of time 712 is two seconds long. The vertical dimension of thebubble would therefore be 1 inch. If the bubble is assumed to bespherical in shape, then the volume of the bubble could be calculated asa sphere having a diameter of 1 inch. The calculated volume of thebubble could be used to calculate a length of time to open a valve for aduct to siphon off a slug of molten glass.

As discussed above, an array of ultrasonic sensors could be used todetect a position of a bubble in the downtube. FIG. 7B illustrates agraph 740 showing measured propagation time 702 on a vertical axis andtime 704 on the horizontal axis. Here, the graph 740 shows measuredpropagation time 702 for a first ultrasonic sensor and a secondultrasonic sensor arranged on opposite sides of the downtube. As shownin FIG. 7B, for a first period of time 770, a first series of datapoints 750 for the first ultrasonic sensor and a first series of datapoints 764 the second ultrasonic sensor have a propagation time 742 ofthe first duration. As shown in FIG. 7B, the duration times detected bythe first ultrasonic sensor and the second ultrasonic sensor could bedifferent or could be the same. Here, for illustration and claritypurposes, the duration times detected by the first ultrasonic sensor andthe second ultrasonic sensor are shown to be different. For a secondperiod of time 772, a second series of data points 752 for the firstultrasonic sensor have a propagation time 746 of a second duration and asecond series of data points 762 for the second ultrasonic sensor have apropagation time 748 of a third duration. Here, the third duration isshorter than the second duration. Then, for the third period of time774, a third series of data points 754 for the first ultrasonic sensorhave a propagation time 742 of the first duration and a third series ofdata points 764 for the second ultrasonic sensor have a propagation time742 of the first duration. The period of time 762 in which thepropagation time 746 for the first ultrasonic sensor is the secondduration and the propagation time 748 for the second ultrasonic sensoris the third duration indicates the presence of a bubble in the moltenglass. Furthermore, because the propagation time 748 of the thirdduration, detected by the second ultrasonic sensor, is less than thepropagation time 746 of the second duration, detected by the firstultrasonic sensor, the detected bubble is closer to the secondultrasonic sensor in the downtube. Again, the third period of time 774in which the propagation times 742 detected by the ultrasonic sensorshas returned to the first duration could indicate that the bubble in themolten glass is no longer being detected.

As discussed above with reference to FIG. 7A, a length of time of thesecond period of time 772 could be used to estimate a vertical size ofthe bubble. Furthermore, the differences in detected propagation time bythe first ultrasonic sensor and the second ultrasonic sensor could beused to estimate a lateral dimension of the bubble. For example, invarious embodiments, the ultrasonic sensors could be calibrated suchthat a particular propagation time corresponds to a particular locationof a boundary of a bubble in the downtube. Such calibration data couldbe used to calculate and/or estimate boundaries of the bubble closest toeach of the ultrasonic sensors to estimate a horizontal size of thebubble.

As discussed above with reference to FIGS. 5A and 5B, four or moreultrasonic sensors could be arranged around the downtube. Such an arrayof ultrasonic sensors could provide a location of a bubble in the moltenglass in the downtube in multiple axes. Also, such an array ofultrasonic sensors could provide a more accurate estimate of a volume ofthe bubble by estimating and/or calculating dimensions of the bubble inthe multiple axes.

The embodiments described above have been discussed with reference tomolten glass 252. In various embodiments, bubbles could be detected andremoved from other molten substrates, such as molten plastic.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

Aspects of the present invention may take the form of an entirelyhardware embodiment, an entirely software embodiment (includingfirmware, resident software, microcode, etc.) or an embodiment combiningsoftware and hardware aspects that may all generally be referred toherein as a “circuit,” “module” or “system.” As discussed above withrespect to various embodiments, a duct in a downtube can be operated bya controller. The controller could include a processor and computermemory. The computer memory could store a computer program that isexecutable by the processor to analyze data from the ultrasonicsensor(s) to detect a bubble in the molten substrate. In response todetecting a bubble, the controller could operate an actuator to open avalve or move a flapper valve, for example. The computer memory couldalso store a program or programs executable by the computer processor tocalculate a size of the bubble and/or a position of the bubble in thedowntube, discussed above.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Smalltalk, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. An apparatus for supplying a molten substrate,the apparatus comprising: a downtube adapted to receive the moltensubstrate at an upstream end of the downtube and to distribute themolten substrate at a downstream end of the downtube; an ultrasonicsensor arranged along the downtube, wherein the ultrasonic sensor isoperable to detect bubbles in the molten substrate in the downtube; anda duct arranged along the downtube, wherein the duct is operable toremove a slug of the molten substrate from the downtube upon theultrasonic sensor detecting a bubble in the molten substrate.
 2. Theapparatus of claim 1, wherein the slug of molten substrate removed fromthe downtube includes the detected bubble.
 3. The apparatus of claim 1,further comprising: a valve arranged in the duct, wherein the valve ismovable between an open position and a closed position, and whereinmolten substrate can pass through the valve when the valve is in theopen position; a vacuum arranged downstream of the valve, wherein thevacuum siphons the slug of molten substrate into the duct when the valveis in the open position; and a controller communicatively connected tothe ultrasonic sensor and programmed to move the valve to the openposition upon receiving a signal representing the ultrasonic sensordetecting the bubble in the slug of molten substrate.
 4. The apparatusof claim 3, further comprising a second ultrasonic sensor arranged alongthe duct downstream of the valve, wherein the second ultrasonic sensoris operable to detect bubbles in molten substrate in the duct, andwherein the controller is communicatively connected to the secondultrasonic sensor and programmed to move the valve to the closedposition upon receiving a signal representing the second ultrasonicdetector detecting the bubble in the duct.
 5. The apparatus of claim 1,further comprising: a diverting valve arranged along the downtube,wherein the diverting valve is movable between a stowed position and adiverting position, and wherein the diverting valve diverts moltensubstrate into the duct when the diverting valve is in the divertingposition; and a controller operable to move the diverting valve to thediverting position upon the ultrasonic sensor detecting the bubble inthe slug of molten substrate.
 6. The apparatus of claim 5, furthercomprising a second ultrasonic sensor arranged along the duct downstreamof the diverting valve, wherein the second ultrasonic sensor is operableto detect bubbles in molten substrate in the duct, and wherein thecontroller is operable to move the diverting valve to the stowedposition upon the second ultrasonic detector detecting the bubble in theduct.
 7. The apparatus of claim 1, further comprising a secondultrasonic sensor arranged along the downtube downstream of the duct. 8.The apparatus of claim 1, wherein the ultrasonic sensor comprises anarray of ultrasonic sensors arranged around a perimeter of the downtube,and wherein the duct is operable to remove the slug of molten substratefrom the downtube upon at least one of the ultrasonic sensors detectingthe bubble in the slug of molten substrate.
 9. The apparatus of claim 8,further comprising a controller operable to detect a position of thebubble in the downtube, and wherein the duct comprises a plurality ofducts arranged around a perimeter of the downtube, wherein the pluralityof ducts include respective valves arranged in the ducts, and whereinthe controller is operable to open at least one of the valves associatedwith at least one duct that is closest to the detected position of thebubble in the downtube.
 10. The apparatus of claim 1, wherein the moltensubstrate comprises one of: molten glass, molten electronic grade glass,and molten plastic.
 11. An apparatus for forming fibers from a moltensubstrate, the apparatus comprising: a furnace operable to melt asubstrate supply into a molten substrate; a downtube that includes anupstream opening and a downstream opening, wherein the upstream openingis in fluid communication with an outlet of the furnace, the downtubeincluding: an ultrasonic sensor arranged along the downtube, wherein theultrasonic sensor is operable to detect bubbles in the molten substratein the downtube; and a duct arranged along the downtube, wherein theduct is operable to remove a slug of molten substrate upon theultrasonic sensor detecting a bubble in the slug of molten substrate; abushing in fluid communication with the downstream end of the downtube,wherein the bushing includes a plurality of extrusion portstherethrough; and a winding apparatus operable to pull threads of moltensubstrate through the extrusion ports and form the threads into awinding of threads.
 12. The apparatus of claim 11, wherein the slug ofmolten substrate removed from the downtube includes the detected bubble.13. The apparatus of claim 11, further comprising a second downtube thatincludes an upstream end opening and a downstream opening, wherein theupstream opening of the downtube is in fluid communication with anoutlet from the furnace, and wherein the downstream opening of thesecond downtube is in fluid communication with the bushing, the seconddowntube including: a second ultrasonic sensor arranged along the seconddowntube, wherein the second ultrasonic sensor is operable to detectbubbles in the molten substrate in the second downtube; and a secondduct arranged along the second downtube, wherein the second duct isoperable to remove a slug of molten substrate upon the second ultrasonicsensor detecting a bubble in the slug of molten substrate in the seconddowntube.
 14. The apparatus of claim 11, wherein the winding apparatuspulls the threads of molten substrate at a reduced rate while the ductremoves the slug of molten substrate.
 15. The apparatus of claim 11,further comprising a second ultrasonic sensor arranged along thedowntube at a downstream location relative to the duct, wherein thesecond ultrasonic sensor is operable to detect bubbles in the moltensubstrate at the downstream location, and wherein the winding apparatusis operable to mark a length of the formed threads after the secondultrasonic sensor detects a bubble in the molten substrate at thedownstream location.